Modify android app source code bought from Codecanyon and integrate payment gateway (Paystack)

I am looking for a freelancer to modify an existing android Taxi app source code bought from Codecanyon and integrate payment gateway (Paystack). The freelancer needs to make modifications on the Android platform and help me set up the payment gateway. I am also open to brainstorming ideas on additional functionality that could be added to the app. This project requires expertise in modifying app source code and incorporating payment gateways. If you think you have the right skills to handle this project, feel free to bid. I'm excited to see the possibilities this project could bring!